Thanks Peteleo, but the bore size actually measures .995. Taking in
consideration the Harbor Freight calipers I was using, I rounded it to
1 inch. I suppose it possible this has been messed with, seeing that
I have two bleeders in it and not one.

You are correct 1' bore. I was thinking the Cortina MK2 is 7/8".
The extra bleed valve could just be used as a plug to prevent moisture from entering. Your picture doesn't show the extended boss were the spring attaches to. I assume it does.

Your s/cyl may have come with an attached clamped bracket as this one for the 100E. Girling produced hydralic cyls that were interchangeable for various makes.
6467376(#) there should be one more digit. I have one s/cyl that reads:
64673768.